Loose lamination die with rotating blanking station

ABSTRACT

In a method and apparatus for rotating loose laminations in a loose lamination die, a strip is fed through the die to a rotatable blanking chamber of a blanking station. There, a punch engages with a die ring to punch a lamination free from the strip. The rotatable blanking chamber is biased in an upwardly direction. When the punch is not engaging with the die ring, the rotatable chamber is in an upward position wherein a gap develops between laminations retained at a bottom of the rotatable chamber, and those laminations lying directly below the rotatable chamber. The rotatable chamber can then be rotated without damage to the laminations at the gap because of the presence of the gap. A finger joint having an upper and lower portion is provided below the rotatable chamber which permits the gap to develop when the rotatable chamber is biased in the upward direction.

This is a division of application Ser. No. 09/609,550, filed Jul. 3,2000.

BACKGROUND OF THE INVENTION

The invention relates to a production of cores for electromechanicaldevices such as motors, and more particularly the production of suchcores by stacking of a plurality of laminations.

It is known to produce cores for electromechanical devices such asmotors by stacking a plurality of laminations to form stators andmatching rotors. Frequently, when forming the rotors or stators by aseries of stacked laminations, the laminations are maintained in a looseconfiguration in a very long stack, thus allowing the motor manufacturerto select a plurality of loose laminations from one end of the stack toform a final stack of a given height for a particular motor application.

It is also known in lamination stacking dies which create finishedstacks of a predetermined height to provide a rotatable chamber wherethe rotors or stators are blanked out so that the laminations of a rotorcan be “indexed”. Indexing typically refers to one or more of thelaminations being rotated by a prescribed angle such as 90 or 180° sothat a varying thickness of the steel strip from which the rotors orstators are punched out does not result in a stack having a tilt, thatis where one side is higher than the other. By rotating one or morelaminations, the stack can be evened out since the indexing willcompensate for the varying strip thickness from one side of the strip tothe other.

Typically, such indexed lamination stacks are produced in stacking dieswhere a prescribed stack having a given number of laminations or for agiven height is produced. However, in the production of looselaminations wherein no particular given stack height is provided, adifficulty arises in indexing such loose laminations for the followingreasons.

High volume production of loose laminations requires the use of a chuteattached to the bottom of a die bolster plate in which the laminationstravel through after being blanked from the die. Due to the weight ofthe laminations in the chute, backpressure is created. To keep the chutebackpressure from forcing the blank laminations back up through the dieopening, “pinch” or “choke” rings are installed in the die. In order tocombine loose lamination indexing with part removal by chutes, aseparation must be made between the laminations in the indexing chamberand those in the chute to prevent lamination damage from occurring asthe index chamber rotates.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a separation asdescribed above so that loose laminations can be successfullyrotationally indexed without causing lamination damage.

According to the present invention, a system and method is provided forrotating one or more laminations relative to other laminations in aloose lamination die. In a punching station for punching laminationsfree from a strip, a rotatable chamber is provided. As the punch engagesthe strip, the rotatable chamber is pushed downwardly. After thelamination has been punched, and as the punch moves upwardly, therotatable chamber returns to its original upward position. In the upwardposition, a gap results between laminations retained at the bottom endof the rotatable chamber and laminations just below the bottom of therotatable chamber. Because of the gap, the rotatable chamber can then berotated without causing damage to the lamination at the bottom of therotatable chamber and the lamination just below the rotatable chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side cross-sectional view taken through a rotatablechamber of a loose lamination die with the die in the cutting orblanking position; and

FIG. 2 is the same cross-sectional view as FIG. 1 but with the die inthe open position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the side cross-sectional view of FIG. 1, a rotating blanking station10 of a loose lamination die is illustrated wherein laminations forrotors or stators are punched out from a steel strip 11. As is known inthe art, prior to the final blanking station for the rotor or stator,other operations have already been performed such as blanking out thecenter hole for the rotor or stator and apertures for slots throughwhich wires may pass.

In FIG. 1, the rotating blanking station 10 is generally illustrated ina side cross-sectional view with a punch 12 in the cutting position forcutting through the strip 11 to produce a rotor or stator lamination.The punch 12 cooperates with a die ring 14 mounted in a rotatablechamber 15 mounted in a die shoe 13 resting on a bolster plate 26 forcutting the rotor or stator free from the steel strip 11. The rotatingand blanking station 10 is mounted in the die shoe 13.

The rotatable chamber 15 is provided having an upper pinch zone 9 whichprovides a pinch fit for the stamped free rotors or stators whichaccumulate within the upper portion of the index chamber 15. The chamber15 is mounted in a ball bearing race 16 having a ball bearing cage 17 toradially position the rotatable chamber. A timing belt pulley 18 isprovided driven by a drive belt 3 on the rotatable chamber 15 forrotation thereof.

Chamber pilot pins 19 are received in apertures 8 to align the punch 12with the die ring 14.

In the bolster plate 26 below the rotatable chamber 15, a finger jointassembly 20 is provided formed of an upper finger joint 21 and a lowerfinger joint 22 along with an upper finger joint retainer 23. Springs 27are provided for biasing the upper finger joint 21 away from the lowerfinger joint 22. The upper finger joint 21 has projecting fingers 32which intermesh with fingers 31 on the lower finger joint. A chute 24connects to the bottom of the lower finger joint 22 with a flange 38 andbolts 40 and 41 received in threaded operation in the flange 38.

With the die in the cutting position, the rotatable chamber 15 ispressed downwardly against the action of the springs 27 so that a gap Ddevelops as shown at 36 and 37, thus illustrating the chamber 15 traveldistance in the downward direction.

As illustrated in FIG. 2, which is the same as FIG. 1 but with the diein the open position (punch 12 spaced upwardly from the die ring 14 withthe chamber pilot pins 19 no longer engaging in the correspondingapertures 8), the springs 27 cause the rotatable chamber 15 to move inan upwardly direction by the travel distance D indicated at 34, and 39until an upper surface of pulley 18 strikes a bottom of a stop surface 2located at an end wall of a pocket in the die shoe 13. In other words,in FIG. 1 the bottom of the rotatable chamber indicated at 25 is rightat the top of the bolster plate 26. However, in FIG. 2, a gap 39 havinga spacing D exists which results in a separation zone 33 betweenlamination stack 33A pinch fit in the pinch zone 4 at the lower portionof rotatable chamber 15, and the lower lamination stack 33B resting butnot pinch fit in the wider portion of the inner aperture 7 of the upperfinger joint 21. Below this wider portion, in a pinch zone 5 having anarrower diameter, the laminations lying below the lower laminationstack 33B are again retained by a pinch fit prior to entry into thechute 24. Thus, when the rotatable chamber 15 rotates, the separationzone 33 prevents damage to the lamination at the bottom of stack 33A andthe lamination at the top of stack 33B.

The method for rotating loose laminations according to the presentinvention will now be described. First, the progressively stamped stripis positioned over the elevated indexing chamber 15. As the die closes,the pilot pins 19 engage the rotatable chamber 15 to align it properly.As the punch 12 stamps through the strip 11 to blank out the rotor, thechamber 15 is pushed down. The rotor or stator lamination is blankedfrom the strip 11 during this time. At this point, no separation zone 33exists between the lamination stack 33A in the rotatable chamber andstack 33B in the finger joint assembly 20 leading to the chute 24 (FIG.1).

As the press travels in the upstroke (see FIG. 2), spring pressure fromsprings 27 forces the upper finger joint 21 upwardly. This also forcesthe rotatable chamber 15 to travel upward within the ball bearing cage17. The ball bearing cage allows for both radial and vertical movementof the chamber. The amount of this chamber travel may vary based onlamination size and/or configuration.

The pinch area 5 in the lower finger joint 22 keeps the chutebackpressure in chute 24 from forcing the lamination stack 33B upward.The pinch zone 4 at the bottom of the index chamber 15 forces thelaminations inside the chamber to travel up with the chamber 15 as itmoves up. The separations zone 33 in FIG. 2 between the laminationstacks 33A and 33B is then formed at the point where the rotatablechamber 15 meets the upper finger joint 21. The rotatable, chamber 15,with pilot pins 19 disengaged with the upward motion of the punch 12, isthen indexed via use of a mechanical indexing box or servo motor notshown via the timing belt pulley 18 engaged by belt 3. The separationbetween the laminations prevents damage between the stationary androtating laminations.

The process above utilizes a blank-through stamping operation. Thisinvention can also be utilized with a cut-off process (corner trim die)or compounded or pad blank stamping operation.

Although various minor modifications might be suggested by those skilledin the art, it should be understood that my wish to embody within thescope of the patent warranted hereon all such modifications asreasonably and properly come with the scope of my contribution to theart.

I claim as my invention:
 1. A loose lamination die, comprising: a dieblock having a blanking station with a vertically moveable rotatablechamber having a die ring; a punch for engaging with a strip at the diering; a biasing member for pushing the rotatable chamber to an upwardposition when the punch is no longer engaging with the strip or diering; and a joint having an upper portion and a lower portion which canvertically separate so that a separation zone occurs between adjacentlaminations when the rotatable chamber is rotated.
 2. A loose laminationdie, comprising: a die block having a blanking station with a rotatablechamber having a die ring at an upper end thereof; a punch for engagingwith the die ring; a retaining member for the rotatable chamberpermitting the rotatable chamber to move in a downward direction as thepunch punches the strip and enters the die ring; a biasing member forpushing the rotatable chamber to an upward position when the punch is nolonger engaging with the strip or die ring; and a joint having an upperportion and a lower portion allowing for vertical separation of theupper and lower portions as the rotatable chamber moves to the upwardposition so that a separation zone occurs between a bottom-mostlamination held in the rotatable chamber and an upper-most laminationjust below a bottom of the rotatable chamber.
 3. The die according toclaim 2 wherein the joint comprises an upper portion and a lower portionhaving respective vertically extending and intermeshing fingers; andsaid biasing member comprising a spring biasing the upper portion in anupward direction so that the rotatable chamber which rests on top of theupper portion is pushed to the upward position.
 4. The die according toclaim 3 wherein a chute is provided beneath the joint, wherein the lowerportion of the joint has an aperture with an inside diameter smallenough to provide a pinch zone for the laminations and the upper portionof the joint has an inside aperture having an inside diameter greaterthan said pinch zone in the lower portion, and wherein the rotatablechamber has a pinch zone at a bottom thereof and a pinch zone at a topthereof with a central portion of the rotatable chamber having a greaterdiameter than the upper and lower pinch zones of the rotatable chamber.5. The die according to claim 2 wherein the joint is provided in abolster plate on which a die shoe containing the rotatable chamber ismounted, and wherein a chute is connected at a bottom of the bolsterplate beneath the joint.
 6. The die according to claim 2 wherein theretaining member comprises a ball-bearing race and a ball-bearing cagefor radially positioning the rotatable chamber.
 7. The die according toclaim 2 wherein the upward position of the rotatable chamber is definedby a top surface of a pulley on the rotatable chamber striking anadjacent stop surface.